This invention relates generally to method and apparatus for closing wounds and more particularly, to a method and apparatus for applying optical energy to biological tissue whereby the tissue is converted to a collagenous, denatured protein substance which joins severed tissues and closes wounds without injurious tissue shrinkage.
Various techniques have been used to repair wounds and closing surgical incisions including suturing, cryogenic, cauterization and tissue welding. Details of these techniques and their drawbacks are described in co-pending patent application Ser. No. 07/639,025, and U.S. Pat. Nos. 5,001,051, 4,854,320 and 4,672,969.
The preferred technique for tissue repair is laser welding. This technique is described in detail in co-pending patent application Ser. No. 07/639,025 and U.S. Pat. Nos. 5,001,051, 4,854,320 and 4,672,969 which are incorporated by reference. In laser welding, the tissue to be welded is heated to a predetermined temperature at which optical energy converts biological tissue into a collagenous substance. The collagenous substance contains bonds which can close closely approximated edges of tissue in a wound or lesion, together. The laser is controlled so that optical energy is converted into thermal energy bounded by a minimum absorption rate at which tissue is converted to a collagenous substance and a maximum absorption above which the water contained in the tissue wound boils.
A drawback to the aforementioned laser surgery technique is that when the laser converts the tissue to a collagenous substance and heated to a high enough temperature, the tissue begins to shrink. This shrinkage may result in disruptions in the bonds within the collagenous substance. A disruption in the bond has been determined to prevent tissue closure from occurring.
Another drawback is when the tissue is heated, a temperature gradient may form in the tissue. Consequently portions of the tissue become hotter than other portions resulting in tissue shrinkage of the hotter portions. Also when welding, the surgeon may position the laser incorrectly injuriously rewelding the area. These additional welding and absorption factors could overheat the tissue causing the tissue to coagulate and disrupt the start and subsequent efficacy of the closure.